On March 26, 2012, the Ohio Department of Agriculture (ODA) announced the discovery of Boxwood Blight in Lake County in northeast Ohio. This was the first detection of Boxwood Blight in the Buckeye State. Boxwood Blight is a disease caused by a fungus (Cylindrocladium pseudonaviculatum) that threatens the health and sustainability of Boxwood plants.
Boxwood Blight was first detected in the US in North Carolina in October of 2011. Plant pathologists in the United Kingdom first identified the disease in the mid-1990s. It is unclear how the disease was introduced into the US. To date, Ohio is the 10th state to identify Boxwood Blight.
This disease is spread primarily by water (rain splash, irrigation, runoff, etc.), by the movement of plant material in the trade, and through contaminated tools, vehicles, boots, etc. Initial symptoms of the disease on Boxwood plants include leaf spots and blights, rapid defoliation, distinctive black cankers on stems, and severe dieback. Most Boxwood plants are not killed by the disease, but will become so defoliated as to be aesthetically unacceptable.
The suspect infection was reported to inspectors with the ODA and the Ohio Plant Diagnostic Network (OPDN) who then sent samples to the USDA APHIS for confirmation. At this time, officials are unsure how the disease was introduced into the northeast Ohio nursery.
Keep in mind there are a number of problems that can be found on Boxwood including volutella stem blight, phytophthora root rot, and frost/freeze injury. If you suspect you are seeing Boxwood Blight, Nancy Taylor with the CWEPPDC urges the samples be submitted for diagnosis. Do not rely on field diagnosis.